/**
 * IK 中文分词 版本 5.0
 * IK Analyzer release 5.0
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 源代码由林良益(linliangyi2005@gmail.com)提供
 * 版权声明 2012，乌龙茶工作室
 * provided by Linliangyi and copyright 2012 by Oolong studio
 */
package org.wltea.analyzer.dic;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

/**
 * 词典树分段，表示词典树的一个分枝
 */
class DictSegment implements Comparable<DictSegment> {
    // 公用字典表，存储汉字
    private static final Map<Character, Character> charMap            = new HashMap<Character, Character>(16, 0.95f);
    // 数组大小上限
    private static final int                       ARRAY_LENGTH_LIMIT = 3;
    // Map存储结构
    private Map<Character, DictSegment>            childrenMap;
    // 数组方式存储结构
    private DictSegment[]                          childrenArray;
    // 当前节点上存储的字符
    private Character                              nodeChar;
    // 当前节点存储的Segment数目
    // storeSize <=ARRAY_LENGTH_LIMIT ，使用数组存储， storeSize >ARRAY_LENGTH_LIMIT ,则使用Map存储
    private int                                    storeSize          = 0;
    // 当前DictSegment状态 ,默认 0 , 1表示从根节点到当前节点的路径表示一个词
    private int                                    nodeState          = 0;

    DictSegment(final Character nodeChar) {
        if (nodeChar == null) {
            throw new IllegalArgumentException("参数为空异常，字符不能为空");
        }
        this.nodeChar = nodeChar;
    }

    Character getNodeChar() {
        return this.nodeChar;
    }

    /*
     * 判断是否有下一个节点
     */
    boolean hasNextNode() {
        return this.storeSize > 0;
    }

    /**
     * 匹配词段
     * 
     * @param charArray
     * @return Hit
     */
    Hit match(final char[] charArray) {
        return this.match(charArray, 0, charArray.length, null);
    }

    /**
     * 匹配词段
     * 
     * @param charArray
     * @param begin
     * @param length
     * @return Hit
     */
    Hit match(final char[] charArray, final int begin, final int length) {
        return this.match(charArray, begin, length, null);
    }

    /**
     * 匹配词段
     * 
     * @param charArray
     * @param begin
     * @param length
     * @param searchHit
     * @return Hit
     */
    Hit match(final char[] charArray, final int begin, final int length, Hit searchHit) {
        if (searchHit == null) {
            // 如果hit为空，新建
            searchHit = new Hit();
            // 设置hit的其实文本位置
            searchHit.setBegin(begin);
        } else {
            // 否则要将HIT状态重置
            searchHit.setUnmatch();
        }
        // 设置hit的当前处理位置
        searchHit.setEnd(begin);
        final Character keyChar = new Character(charArray[begin]);
        DictSegment ds = null;
        // 引用实例变量为本地变量，避免查询时遇到更新的同步问题
        final DictSegment[] segmentArray = this.childrenArray;
        final Map<Character, DictSegment> segmentMap = this.childrenMap;
        // STEP1 在节点中查找keyChar对应的DictSegment
        if (segmentArray != null) {
            // 在数组中查找
            final DictSegment keySegment = new DictSegment(keyChar);
            final int position = Arrays.binarySearch(segmentArray, 0, this.storeSize, keySegment);
            if (position >= 0) {
                ds = segmentArray[position];
            }
        } else if (segmentMap != null) {
            // 在map中查找
            ds = segmentMap.get(keyChar);
        }
        // STEP2 找到DictSegment，判断词的匹配状态，是否继续递归，还是返回结果
        if (ds != null) {
            if (length > 1) {
                // 词未匹配完，继续往下搜索
                return ds.match(charArray, begin + 1, length - 1, searchHit);
            } else if (length == 1) {
                // 搜索最后一个char
                if (ds.nodeState == 1) {
                    // 添加HIT状态为完全匹配
                    searchHit.setMatch();
                }
                if (ds.hasNextNode()) {
                    // 添加HIT状态为前缀匹配
                    searchHit.setPrefix();
                    // 记录当前位置的DictSegment
                    searchHit.setMatchedDictSegment(ds);
                }
                return searchHit;
            }
        }
        // STEP3 没有找到DictSegment， 将HIT设置为不匹配
        return searchHit;
    }

    /**
     * 加载填充词典片段
     * 
     * @param charArray
     */
    void fillSegment(final char[] charArray) {
        this.fillSegment(charArray, 0, charArray.length, 1);
    }

    /**
     * 屏蔽词典中的一个词
     * 
     * @param charArray
     */
    void disableSegment(final char[] charArray) {
        this.fillSegment(charArray, 0, charArray.length, 0);
    }

    /**
     * 加载填充词典片段
     * 
     * @param charArray
     * @param begin
     * @param length
     * @param enabled
     */
    private synchronized void fillSegment(final char[] charArray, final int begin, final int length, final int enabled) {
        // 获取字典表中的汉字对象
        final Character beginChar = new Character(charArray[begin]);
        Character keyChar = DictSegment.charMap.get(beginChar);
        // 字典中没有该字，则将其添加入字典
        if (keyChar == null) {
            DictSegment.charMap.put(beginChar, beginChar);
            keyChar = beginChar;
        }
        // 搜索当前节点的存储，查询对应keyChar的keyChar，如果没有则创建
        final DictSegment ds = this.lookforSegment(keyChar, enabled);
        if (ds != null) {
            // 处理keyChar对应的segment
            if (length > 1) {
                // 词元还没有完全加入词典树
                ds.fillSegment(charArray, begin + 1, length - 1, enabled);
            } else if (length == 1) {
                // 已经是词元的最后一个char,设置当前节点状态为enabled，
                // enabled=1表明一个完整的词，enabled=0表示从词典中屏蔽当前词
                ds.nodeState = enabled;
            }
        }
    }

    /**
     * 查找本节点下对应的keyChar的segment *
     * 
     * @param keyChar
     * @param create
     *            =1如果没有找到，则创建新的segment ; =0如果没有找到，不创建，返回null
     * @return
     */
    private DictSegment lookforSegment(final Character keyChar, final int create) {
        DictSegment ds = null;
        if (this.storeSize <= DictSegment.ARRAY_LENGTH_LIMIT) {
            // 获取数组容器，如果数组未创建则创建数组
            final DictSegment[] segmentArray = this.getChildrenArray();
            // 搜寻数组
            final DictSegment keySegment = new DictSegment(keyChar);
            final int position = Arrays.binarySearch(segmentArray, 0, this.storeSize, keySegment);
            if (position >= 0) {
                ds = segmentArray[position];
            }
            // 遍历数组后没有找到对应的segment
            if ((ds == null) && (create == 1)) {
                ds = keySegment;
                if (this.storeSize < DictSegment.ARRAY_LENGTH_LIMIT) {
                    // 数组容量未满，使用数组存储
                    segmentArray[this.storeSize] = ds;
                    // segment数目+1
                    this.storeSize++;
                    Arrays.sort(segmentArray, 0, this.storeSize);
                } else {
                    // 数组容量已满，切换Map存储
                    // 获取Map容器，如果Map未创建,则创建Map
                    final Map<Character, DictSegment> segmentMap = this.getChildrenMap();
                    // 将数组中的segment迁移到Map中
                    this.migrate(segmentArray, segmentMap);
                    // 存储新的segment
                    segmentMap.put(keyChar, ds);
                    // segment数目+1 ， 必须在释放数组前执行storeSize++ ， 确保极端情况下，不会取到空的数组
                    this.storeSize++;
                    // 释放当前的数组引用
                    this.childrenArray = null;
                }
            }
        } else {
            // 获取Map容器，如果Map未创建,则创建Map
            final Map<Character, DictSegment> segmentMap = this.getChildrenMap();
            // 搜索Map
            ds = segmentMap.get(keyChar);
            if ((ds == null) && (create == 1)) {
                // 构造新的segment
                ds = new DictSegment(keyChar);
                segmentMap.put(keyChar, ds);
                // 当前节点存储segment数目+1
                this.storeSize++;
            }
        }
        return ds;
    }

    /**
     * 获取数组容器
     * 线程同步方法
     */
    private DictSegment[] getChildrenArray() {
        if (this.childrenArray == null) {
            synchronized (this) {
                if (this.childrenArray == null) {
                    this.childrenArray = new DictSegment[DictSegment.ARRAY_LENGTH_LIMIT];
                }
            }
        }
        return this.childrenArray;
    }

    /**
     * 获取Map容器
     * 线程同步方法
     */
    private Map<Character, DictSegment> getChildrenMap() {
        if (this.childrenMap == null) {
            synchronized (this) {
                if (this.childrenMap == null) {
                    this.childrenMap = new HashMap<Character, DictSegment>(DictSegment.ARRAY_LENGTH_LIMIT * 2, 0.8f);
                }
            }
        }
        return this.childrenMap;
    }

    /**
     * 将数组中的segment迁移到Map中
     * 
     * @param segmentArray
     */
    private void migrate(final DictSegment[] segmentArray, final Map<Character, DictSegment> segmentMap) {
        for (final DictSegment segment : segmentArray) {
            if (segment != null) {
                segmentMap.put(segment.nodeChar, segment);
            }
        }
    }

    /**
     * 实现Comparable接口
     * 
     * @param o
     * @return int
     */
    @Override
    public int compareTo(final DictSegment o) {
        // 对当前节点存储的char进行比较
        return this.nodeChar.compareTo(o.nodeChar);
    }
}
